[llvm] [LV] Remove selectUserVF, remove use of legacy expectedCost (NFCI) (PR #191216)

[via llvm-commits]

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@@ -4994,15 +4987,7 @@ InstructionCost LoopVectorizationCostModel::computePredInstDiscount(
 
 InstructionCost LoopVectorizationCostModel::expectedCost(ElementCount VF) {
   InstructionCost Cost;
-
-  // If the vector loop gets executed exactly once with the given VF, ignore the
-  // costs of comparison and induction instructions, as they'll get simplified
-  // away.
-  SmallPtrSet<Instruction *, 2> ValuesToIgnoreForVF;
-  auto TC = getSmallConstantTripCount(PSE.getSE(), TheLoop);
-  if (TC == VF && !foldTailByMasking())
-    addFullyUnrolledInstructionsToIgnore(TheLoop, Legal->getInductionVars(),
-                                         ValuesToIgnoreForVF);
+  assert(VF.isScalar() && "must only be called for scalar VFs");
 
   // For each block.
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ayalz wrote:

```suggestion
```
goes w/o saying

https://github.com/llvm/llvm-project/pull/191216